<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>绝对定位</title>
    <style type="text/css">
        body{
            border: 1px solid orange;
            margin: 0px;
            padding: 0px;
            width: 100%;
            height: 400px;
        }
        div{
            width: 200px;;
            height: 200px;
        }
        div.father{
            width: 100%;
            height: 400px;
            border: 1px solid blue;
            position: absolute;
            top: 50px;
            left: 50px;
        }
        div.one{
            background-color: red;
            position: absolute;
            top: 200px;
        }
        div.two{
            width: 400px;
            background-color: green;
            position: absolute;
            top: 20px;
            left: 20px;
        }
        div.three{
            background-color: blue;
            position: absolute;
            top: 200px;
            left: 200px;
        }
    </style>
</head>
<body>
    <!-- 
        特点:
            1.脱离标准文档流 不再页面上占位置
            2.层级提高 压盖现象
            3.参考点以左上角 子绝父相
    -->
    <div class="father">
        <div class="one">one</div>
        <div class="two">two</div>
        <div class="three">three</div>
    </div>
</body>
</html>